EFFECTS OF SOME ORGANIC SOLVENTS ON GP lb AND ACTIN-BINDING PROTEIN IN BLOOD PLATELETS
Effects on filamentous proteins appear to be a central phenomenon in the neuronal toxic effects of organic solvents. We have therefore compared the effects of some organic solvents (particularly isopropylalcohol, IPA) to the previously observed effects of dibucaine (DBC) on platelet cytoskeletal proteins. Incubation of platelets with 6% IPA at 37° C, like DBC, initiates a degradation of actin-binding protein (ABP) as substrate for a calcium activated protease (CAP), shown by SDS-PAGE. IPA leads to an increase followed by a decrease in bovine von Willebrand factor-induced agglutination. The decrease is accompanied by a release of glycocali-cin from the GP lb α-chain. The process was also studied using CIE of Triton X-100 extracts of platelets against antiserum to glycocalicin. Incubation of platelets with IPA before extraction in the presence of 4.2 mM leupeptin leads to a time-dependent transformation of GP Ib-related immunoprecipitates from that of the slow-migrating peak III complex (probably between ABP and GP lb) to the faster migrating GP Ib-precipitate. Our working hypothesis is that IPA induces an activation of the CAP by mobilizing calcium. This leads to degradation of ABP and liberation of GP lb from the cytoskeleton accompanied by an increased tendency for agglutination. The following decrease is explained by degradation of the glycocalicin part of the GP lb enchain which contains the binding-site for von Willebrand factor. We conclude that IPA has a similar effect on GP lb and ABP as DBC. Preliminary studies with 1% DMSO and 0,005% toluene at 37° C revealed that these organic solvents have some similar effects on platelets as described for IPA. Possibly the described effects are characteristic of certain cells at an early stage in a process ultimately leading to cell lysis.